1. Field of the Invention
The invention relates in general to methods and devices for aligning adjacent plates prior to joining them together by welding, brazing, adhesive bonding, or the like.
2. Description of the Prior Art
In the field of welding, a number of clamping devices have been invented to serve the purpose of metal plate alignment. Daubon U.S. Pat. No. 4,513,955 proposes the expedient of an L-shaped member in which a working screw is threaded through one arm to apply pressure on one plate while the other arm is bolted to an angle bracket that is removably tack welded to the other plate. Varga U.S. Pat. No. 3,556,508 proposes a similar expedient except that the L-shaped member is welded to a flat bed and an adjusting screw is threadably mounted in the bed. The flat bed with the permanently mounted L-shaped member is removably tack welded to the plate. These proposed expedients require a specially manufactured flat bed or bracket that has a limited life because of the effects of repeatedly tack welding, breaking, and re-welding it in the same place. Both Varga and Daubon require the use of screws and threaded holes in the same mounting bracket that is consumed by repeated welding in the same spot. The tools for forming threads in holes are typically not immediately available to a welder at the job site where large plates are being welded together. Likewise, the removal and insertion of screws in clamps interrupts the flow of work and slows down the operation. If a small screw is lost it is often not immediately replaceable on a job site.
Conventional practice often comprises just cutting a C-clamp in half to form an L-shaped member much like that shown in Varga. The cut stub is then removably tack welded directly to a plate. Some part of the stub is consumed every time it is tack welded and then broken away from a plate, so the life of the tool is limited. The clamp itself is part of the tool so that when the bed or bracket is tack welded to a plate the clamp may be in the way or it may suffer damage during the welding.
Other prior proposed plate alignment expedients include, for example, Neuhaus, Apparatus for Clamping and Aligning Plates or the Like, U.S. Pat. No. 2,672,839, Howe, Welding Clamps, U.S. Pat. No. 3,342,479; and Minix, Alignment Clamp, U.S. Pat. No. 4,108,346. In general, these other proposed clamping devices are relatively complicated in design, difficult to manipulate, and subject to being easily damaged by the welding operation. In fact, the complicated designs make these devices more costly and time consuming to setup, remove, and maintain. Furthermore, many of these prior devices use a metal rod or a metal strap to feed through a thin gap between the plates to pull in a clamping member behind or underneath the plates to force the alignment. If the two plates are of different thickness, the upper or outer surfaces of the plates will not be brought into perfect alignment by the pulling/pushing force of the clamping member. Under such a situation, there is no way to make the adjustments that are necessary to achieve perfect alignment between the plates. Additionally, after the alignment is achieved and welding is completed, the metal rod or strap with the clamping member has to be removed from behind or underneath the plates. In some occasions, this may be very difficult or even impossible to do, especially where the welded plate is very large and heavy, or it forms part of a closed container. Another inconvenience of these proposed prior art expedients is that the holes left behind after the removal of the metal rods or metal straps have to be welded again to complete the job.
These and other difficulties of the prior art have been overcome according to the present invention.